The document by Knunyants et al., Journal of the USSR Academy of Sciences, Chemistry Department, “Reactions of fluoro-olefins”, Report 13, “Catalytic hydrogenation of perfluoro-olefins”, 1960, describes the substantially quantitative hydrogenation of hexafluoropropene (HFP) over a catalyst based on palladium supported on alumina, the temperature changing from 20° C. to 50° C. and then being maintained at this value.
1,1,1,2,3,3-Hexafluoropropane is of use in the manufacture of 1,2,3,3,3-pentafluoropropene.
The tests of the abovementioned prior art were carried out on the laboratory scale and the documents are entirely silent with regard to the lifetime of these catalysts.
The hydrogenation reaction as described above is highly exothermic and presents problems on the industrial scale. This high exothermicity is harmful to the lifetime of the catalyst.
The presence of a compound other than the reactants in the reaction stream can also be the cause of a rapid deactivation of the catalyst.
Furthermore, the document EP 1 916 232 provides a reaction for the multistage hydrogenation of an olefinic compound in order to obtain a high conversion and a high selectivity. Example 1 describes the reaction for the staged hydrogenation of hexafluoropropene in the presence of a catalyst supported on charcoal in four reactors with a temperature of the gas stream at the outlet of the first reactor of 66° C., a temperature of 104° C. at the outlet of the second reactor (for a conversion of 40%), a temperature of 173° C. at the outlet of the third reactor and a temperature of 100° C. at the outlet of the fourth reactor. Cooling stages are provided between the reactors with a temperature of the first bath of 55° C. and a temperature of the second bath of 111° C.
The process as described in the document EP 1 916 232 is expensive in terms of capital cost and, in addition, it is not easy to carry it out.